Scientists unsure why Black lung disease poses greater threat to miners in southwest Va.

(AP) Black lung disease is posing a greater threat to coal miners in far southwest Virginia, and scientists aren't sure why.

A report released by the U.S. Centers for Disease Control and Prevention shows that the number of cases of black lung disease is rising in Lee and Wise counties and that the cases are more severe. Scientists are still analyzing data from Dickenson, Russell, Tazewell and Buchanan counties.

Black lung disease _ known medically as coal workers' pneumoconiosis _ is caused by inhalation of coal dust. After a federal law was passed in 1969 setting dust limits to protect miners' health, the number of miners who developed the disease decreased, according to the study.

"Something doesn't add up, because we're seeing lots more disease than would be expected at those levels of dust," said Vinicius Antao of the National Institute for Occupational Safety and Health, the lead researcher on the project.

The study, published last month in the CDC's Morbidity and Mortality Weekly Report, built on 2003 research that showed pockets where black lung disease was progressing rapidly, particularly in southwest Virginia and eastern Kentucky.

The increase both in the number of cases and their severity "justifies a comprehensive assessment of current dust-control measures," the recent report said.

Researchers examined 328, or 31 percent, of some 1,055 coal miners who were working underground in Lee and Wise in March and May of this year. They ranged in age from 21 to 63 and had worked in the mines for an average of 23 years.

Thirty of the miners had evidence of black lung, and 11 of the cases were advanced, according to the report.

The miners with the advanced cases had an average age of 51 and had spent an average of 31 years working in underground coal mines.

Researchers suggested several possible reasons for the increase and severity of the black lung cases: that the allowable dust limit may be too high; that the levels of coal dust reported may be underestimated; and that the toxicity of the coal being mined may be higher.

The theory used to be that black lung disease would disappear if coal dust was controlled, said Dr. Randy Forehand, a respiratory medicine specialist at Lewis-Gale Medical Center in Salem who has treated black lung patients for 16 years in Richlands in Tazewell County.

"Overall, the levels (of coal dust) and incidences (of black lung disease) are going down, except in these hot spots," Forehand said.

National Institute for Occupational Safety and Health investigators have suggested that they are seeing more cases of miners with black lung disease in small, nonunion mines.

Genetics also plays a role in who develops black lung disease, Forehand said.

"Not everybody who works down there gets it," he said.